Water filled barriers are commonly used on roadways as crashworthy protection devices. Although these barriers may be used to separate traffic and even in some instances to act as crashworthy end terminals to protect the ends of barriers, they are typically used as temporary barriers to protect workers in roadway work zones. Water filled barriers are well suited to this role as they are lightweight and easy to move when empty, making them easy to install quickly, without forklifts, cranes, or other heavy equipment.
In a typical work zone installation, the water filled barriers are offloaded from a transport truck and then placed end to end, allowing them to be pinned together. Some barrier designs have joints with a small amount of compliance, allowing the barriers to conform to curves in the roadway or to conform to the shape of the work zone. Once the barriers have been located and pinned together, a water truck drives from barrier to barrier and a road worker fills each barrier with water, giving it the necessary mass.
Crash testing is used to qualify the performance of water filled barriers before they are able to be used as protection devices. Typically a crash test standard, such as NCHRP 350, or MASH is used to determine the speeds and angles of the crash test vehicles. These test standards also contain pass/fail criteria and many governmental agencies allow the use of water filled barriers based on successfully passing crash tests called out by these standards.
The test standards also allow vehicles to be tested at various speeds, depending upon the anticipated use of the products being tested. For instance, a water filled barrier may be used in low speed applications, such as a parking garage, where it is unlikely to be impacted at greater than 50 kph (31 mph). Under the NCHRP 350 test standard, this speed would correspond to Test Level 1. Likewise, a water filled barrier may be used in a work zone inside the city limits, where posted speeds are closer to 70 kph (48 mph). Under the NCHRP 350 test standard, this speed would correspond to Test Level 2.
One measurement that is taken during the crash testing of water filled barriers is the maximum lateral deflection. This value provides a guideline as to how much room must be left behind the barrier in case of a lateral impact into the barrier. For instance, the Triton® Water filled Barrier, disclosed in U.S. Pat. No. 5,425,594 to Krage, the entire disclosure of which is hereby incorporated herein by reference, exhibited a deflection of 3.8 m (12.8 ft.) during a NCHRP 350 test. The deflection of the Triton barrier may be reduced or increased if impacted by vehicles with different weights, speeds, or impact angles. In addition to the parameters of the impact, listed above, the deflection of a water filled barrier is also dependent upon the design of the barrier itself.
The deflections listed above for the Triton Barrier may be sufficient for many applications, however there may be some work zones where lower values of deflection are desired. Since one of the factors affecting the deflection of a water filled barrier is the stiffness of its joints, one way of reducing a water filled barrier's deflection is to increase the joint stiffness. For instance James in US 2010/0215427 discloses a barrier that uses two joining pins instead of one, stiffening the joint between the barriers significantly. James also discloses a method of decreasing the joint stiffness in key barriers by only engaging one of the pin holes in a barrier. This allows the barriers to follow a radius, for instance to follow a curve in the roadway. Although the James design provides a way of stiffening the barriers by providing two pins, both of these pins are located on the centerline of the barrier. This means that to provide increased joint stiffness, the pins would need to be spaced further apart, increasing the length of the joint. The pins of the James design also do not provide a way of ensuring a stiff joint when the joint is in a curved orientation.